Most Americans paid little attention to the dangers of terrorism until al-Qaida 's September 11th, 2001 terrorist attacks on New York and Washington that killed thousands. But political violence is hardly new. In part one of this three-part series on the roots of terrorism, Leta Hong Fincher takes a look at how modern terrorism has evolved.

The bipartisan commission investigating the September 11th attacks said the United States was completely unprepared for what happened that day.

Yet, Thomas Kean, chairman of the commission, said the attacks should not have been a surprise.

THOMAS KEAN

"We did not grasp the magnitude of a threat that had been gathering over a considerable period of time. As we detail in our report, this was a failure of policy, management, capability, and above all, a failure of imagination."

But terrorists had been using their imagination for a long time.

Bruce Hoffman, terrorism expert at the RAND Corporation “think tank” in Washington D.C., says ever since the reign of terror during the French revolution at the end of the 18th century, terrorist groups have had clear objectives.

BRUCE HOFFMAN

"One sees that terrorism was animated primarily by secular goals, whether it was ethno-nationalist separatism -- in other words the creation or restoration of an historic homeland or creation of a new state -- or very ideological goals, Marxist, Leninist, Maoist, right-wing authoritarian, totalitarian."

Two examples of these traditional terrorist organizations are the paramilitary group, the Irish Republican Army, or IRA, and the Basque separatist organization, ETA.

The IRA carried out bombings and murders with the goal of independence for all of Ireland from Britain.

ETA killed politicians and set off bombs to bring attention to its goal of independence from Spain.

But Mr. Hoffman says, over the past 20 years new terrorist networks have emerged that are much more loosely defined and trans-national. They are amorphous and have cells in dozens of countries.

In 1979, an Islamic revolution in Iran brought the Ayatollah Khomeini to power, setting in motion a rise in Shia Islamic extremism. Iran later sponsored groups such as the Lebanese Hezbollah, which the U.S. government considers a terrorist organization.

Also in 1979, the Soviet army invaded Afghanistan. In response, Saudi-born Osama bin Laden joined the Afghan resistance -- or mujahedeen-- who were mainly Sunni Muslims.

In the 1980s, the U.S. Central Intelligence Agency helped train and equip mujahedeen fighting against Communism. By 1988, bin Laden had formed his new group, al-Qaida , from former mujahedeen and other supporters.

Some analysts say these Muslim fighters were emboldened by their success in driving the Russians out of Afghanistan. With the defeat of the Soviet Union, bin Laden and his network turned their attention to the United States and its allies in the Middle East.

Terrorism expert Bruce Hoffman says bin Laden's goals are ambitious: to wage a holy war for Islam against Western culture.

BRUCE HOFFMAN

"Certainly he seeks to eviscerate U.S. and western influence from Muslim lands. Certainly he works toward the destruction of what he sees as authoritarian, anti-Islamic, corrupt governments throughout the world as well as the destruction of the state of Israel."

Bin Laden's message resonates with millions of Muslims in the Middle East and elsewhere who are angry with the United States.

Omer Taspinar is a scholar of Islam at the Brookings Institution “think tank” in Washington D.C. Mr. Taspinar says that in the eyes of many impoverished Muslims, bin Laden has become a hero who fights on behalf of the poor and disenfranchised.

OMER TASPINAR

"They're unhappy with the way their countries are run and they see their leaders, authoritarian leaders especially in Saudi Arabia and Egypt, are friendly dictators to the United States. Therefore they don't buy the rhetoric that the United States wants to spread democracy to the Middle East when they see the administration in Washington is friendly toward authoritarian regimes in the Middle East."

But not all such regimes. President Bush ordered the invasions of Iraq and Afghanistan as part of the war on terrorism.

PRESIDENT BUSH

"Freedom and democracy in the place that has bred resentment and terror is in our national interests. A free Iraq will help change the world. A free Iraq will help change a neighborhood that needs to be changed."

President Bush says the United States is winning the war on terrorism. His critics disagree. Benjamin Barber is a democracy expert at the University of Maryland.

BENJAMIN BARBER

"The problem with the Bush administration's claim that it's winning the war on terrorism is that it's not fighting a war on terrorism; it's fighting a war on rogue states. I would say it's winning the war on rogue states. It's defeated Taleban Afghanistan, it's defeated Saddam's Baathist Iraq -- the question is, does the defeat of rogue states have anything to do with defeating terrorism? I'm afraid the answer is no."

Mr. Barber says terrorists have become part of the international infrastructure, which makes it impossible to defeat them by military force alone. He and other experts say the threat of Islamist terrorism can only be controlled by addressing the underlying conditions that allow terrorism to thrive.